from 143 to 245 d (same weather Evaluation of Rootstocks on Harvest Metrics of stations as aforementioned), making ‘Pinot Noir clone 02A’ Wine Grapes in Maritime frost risk for most of the AVA a non- major threat. Western Washington The average heat accumulation in the area ranged from less than 1100 1,4 2 3 to just greater than 2000 growing Michelle M. Moyer , Jaqueline King , and Gary Moulton degree days (GDD), base 50 F (‘‘Sequim’’ and ‘‘Seattle’’ stations, re- ADDITIONAL INDEX WORDS. maritime wine grapes, wine grape rootstocks, Vitis spectively); however, 2000 GDD is vinifera generally considered the minimum heat units necessary to ripen tradi- SUMMARY. The Puget Sound American Viticulture Area (AVA), located west of the tional wine grape varieties (Amerine Cascade Mountain Range in Washington State, is a large and uniquely situated area with and Winkler, 1944; Moyer et al., diverse topography and mesoclimates. Given the young age of the AVA, little formal information exists on the appropriate rootstock–scion combination in wine grapes (Vitis 2014). Thus, heat accumulation in vinifera) for the region. This project reports on a series of rootstock trials from 2003 to the growing region is a potential pro- 2007, which evaluated the influence of ‘420A Millardet et de Grasset’, ‘3309 Couderc’, duction limitation in this AVA. To ‘101-14 Millardet et de Grasset’ (all Vitis hybrids), and a self-rooted control on basic help mitigate the challenges posed by harvest metrics of the wine grape scion ‘Pinot noir clone 02A’. At the warmer site in a cooler growing season, research on Everson, WA, rootstocks had no effect on final juice harvest metrics measured by soluble short-season/cool-tolerant varieties solids, titratable acidity (TA), and pH. At the cooler site in Mount Vernon, WA, the began in the 1970s at Washington use of rootstocks did not always influence soluble solids or pH but did reduce final State University’s Northwest Research harvest TA, a desired effect for the region that is typified by low sugar–high TA wines. and Extension Center in Mount Even with a reduction in TA in some rootstock–scion combinations, overall, TA Vernon, WA. These wine grape trials remained at the upper end or above the range typically desired for many wine styles. provided essential information to commercial wine grape producers acific northwestern North major metropolitan areas of Portland, on the best varieties for production America is the largest wine OR; Seattle, WA; and Vancouver, in this climate. As a result of this Pgrape production region out- BC, Canada. research, white-fruited varieties such side of California, with over 86,000 The Puget Sound AVA is char- as Siegerrebe, Madeleine Angevine, acres spread across Washington, Ore- acterized by its diversity in climates and Muller-Thurgau (all V. vinifera) gon, and British Columbia [Bremmer and is the only Washington AVA have already proven successful in and Bremmer, 2014; U.S. Depart- located west of the Cascade Moun- commercial production. ment of Agriculture (USDA), 2012, tains. To highlight this diversity, A renewed interest in variety tri- 2017]. There are 55,445 acres of weather (Washington State Univer- als occurred in the early 2000s, with wine grapes in Washington, of which sity, 2018) from extreme areas in this the focus on addressing the potential 99.8% lay east of the Cascade Moun- AVA in 2012 are described below. threat of phylloxera (Daktulosphaira tains (USDA, 2017). However, there The year 2012 was chosen, as the vitifoliae), the shift in wine consumer is a growing industry in the Puget grape and wine industry across the preference to red wine (Olsen et al., Sound AVA, which is climatologically state of Washington tends to charac- 2006), and the related increase in similar to most of the Oregon wine terize that year as ‘‘average’’ in terms price premiums associated with red grape production areas. This AVA is of temperature and precipitation. varietals. Specifically, there was an one of the largest in total available Rainfall in the region ranged from interest in the Puget Sound AVA to area, encompassing over 4.75 million 14.4 to 60.13 inches (‘‘Sequim’’ and produce ‘Pinot Noir’ after seeing the acres, but contains only 102 acres of ‘‘Tumwater SW’’ stations, respec- success of the variety in Willamette wine grapes (USDA, 2017). From tively). The rainfall pattern is domi- Valley, OR. However, the cool grow- a wine marketing standpoint, it is nated by winter precipitation; low ing season of the Puget Sound AVA one of the best-situated AVAs, given summer precipitation in some years posed challenges in adequately and that it includes or neighbors the typically results in the need for sup- consistently ripening ‘Pinot Noir’ and plemental irrigation. Modified by the controlling vine canopy development Support for this project was provided by the Wash- Pacific Ocean, the frost-free period in which resulted in very large vines with ington State Grape and Wine Research Program and the AVA averages at 188 d but ranges overshaded fruit. The lack of control the Northwest Center for Small Fruit Research. 1Department of Horticulture, Washington State University-Irrigated Agriculture Research and Exten- Units sion Center, Prosser, WA 99350 To convert U.S. to SI, To convert SI to U.S., 2Department of Horticulture, Washington State multiply by U.S. unit SI unit multiply by University-Northwest Research and Extension Cen- ter, Mount Vernon, WA 98273 1 % g/100 mL 1 0.4047 acre(s) ha 2.4711 3 Formerly Department of Horticulture, Washington 29.5735 fl oz mL 0.0338 State University-Northwest Research and Extension 0.3048 ft m 3.2808 Center, Mount Vernon, WA 98273 2.54 inch(es) cm 0.3937 4Corresponding author. E-mail: michelle.moyer@ 0.4536 lb kg 2.2046 wsu.edu. 1.6093 mile(s) km 0.6214 https://doi.org/10.21273/HORTTECH04170-18 ( F – 32) O 1.8 F C( C · 1.8) + 32
830 • December 2018 28(6) over the timing of water application due to rainfall patterns in the area lim- ited the greatest tool in canopy man- agement: deficit irrigation (Wample and Smithyman, 2002). However, the use of rootstocks may help over- come these challenges associated with pest resistance, timing of ripening, and canopy management, thus expand- ing the range of areas where high quality red wine such as ‘Pinot Noir’ can be produced. The trial described herein aimed to look at the influence of rootstocks on the harvest parame- ters of ‘Pinot Noir 02A’. Rootstocks used in this study were selected for pest resistance, for their potential to advance fruit maturity or influence fruit composition, and/or control vine vigor (Bettiga et al., 2003; Catlin, 1991; Reynolds and Wardle, 2001; Ruhl et al., 1988; Shaffer et al., 2004), but only the effects on fruit maturity are discussed in this report.
Materials and methods WEATHER DATA. Temperature data were collected using local tem- perature loggers (RH-52; Avatel Technologies, Brandon, FL) at each of the vineyard sites (site-specific in- formation reported below). Growing degree day unit accumulation was calculated from 1 Apr. to 31 Oct. for each year, using 50 F as a base temperature. To calculate GDD units per day, the base temperature was subtracted from the average daily temperature. In the event that this calculation resulted in a negative num- Fig. 1. Monthly average minimum temperature, maximum temperate, and total ber, the calculated negative number precipitation from AgWeatherNet Stations (Washington State University, 2018) was reset to zero. Figure 1 also displays nearest the research sites of Mount Vernon, WA [WSU Mount Vernon (left column)], and Everson, WA [Nooksack (right column)] for the years of 2004–07; the monthly average minimum and L O maximum temperatures, and total ( F 32) 1.8 = C, 1 inch = 2.54 cm. precipitation that were recorded at AgWeatherNet stations nearest the research sites. These stations included its general early-ripening behavior [3309C (Vitis riparia · V. rupestris ‘‘WSU Mount Vernon,’’ which was and widespread planting in similar selected for phylloxera resistance, low less 0.6 miles from the Mount Vernon climate areas (i.e., western Oregon). to moderate vigor, adaption to deep research site, and ‘‘Nooksack,’’ which The primary goal was to deter- soils, and ease of propagation)], and was within 6 miles of the Everson site mine if rootstocks could advance vine 3) ‘101-14 Millardet et de Grasset’ and was the only AgWeatherNet sta- phenology (specifically, ripening) to [101-14 Mtg (V. riparia · V. rupest- tion that was installed in that area at combat limitations of a cooler grow- ris selected for phylloxera resistance, the time of the study. ing season. The following rootstocks moderate vigor, adaption to deep ROOTSTOCK EVALUATION TRIALS. were used for evaluation; secondary soils, and ease of propagation)]. Self- To consistently evaluate the influence considerations for rootstock selec- rooted vines were used as control. of rootstock on scion development, tions are also listed: 1) ‘420A Mill- Before the selection of these three the same variety clone of Pinot Noir ardet et de Grasset’ [420A (Vitis rootstocks, an additional minitrial of was used across both locations and berlandieri · Vitis rupestris selected rootstocks which also included ‘Riparia all rootstocks. ‘Pinot Noir 02A’ for phylloxera resistance, low vigor, Gloire’ (V. riparia), ‘44-53 Malegue’ (Wadenswil clone Bl 10/16), a adaption to fertile soils, and ease of [V. riparia · (Vitis cordifolia · V. Swiss-origin clone, was selected for propagation)], 2) ‘3309 Couderc’ rupestris)], ‘Teleki 5C’ (V. berlandieri ·
• December 2018 28(6) 831 PRELIMINARY AND REGIONAL REPORTS
V. riparia), and ‘Kober 5BB’ (V. completed in late July and again in STATISTICAL ANALYSES. All data berlandieri · V. riparia) was con- late August to facilitate the installa- were analyzed using JMP statistical ducted. However, because of lack of tion of bird netting. Experimental software (version 9; SAS Institute, performance, these rootstocks were design in both locations was a ran- Cary, NC). Data were analyzed using removed from evaluation. Initial ob- domized block design. Each treat- linear mixed models with replication servations indicated these discarded ment included five adjacent vines per as a random effect. Tukey’s honest rootstocks performed better than self- treatment replication, replicated significant difference test was used for rooted vines, but inferior to the three across three vineyard rows (i.e., one mean separation, with significance at aforementioned varieties (data not treatment replication per row). a = 0.05. shown). Washington State has strict Trials were evaluated in 2004 plant quarantines, and as such, estab- and 2005 in Everson and from 2004 Results and discussion lished populations of phylloxera have through 2007 in Mount Vernon. WEATHER. The recorded GDD not been reported within the state, Juice soluble solids, pH, and TA were accumulation for both Mount Ver- although populations have been re- evaluated in all years. Yield per vine non and Everson is presented in Table ported in Willamette Valley, OR; this was collected in 2006 and 2007. 1. Additional years of temperature allows for the planting of self-rooted Dormant pruning weights, a reflec- data beyond the years of this study vines within the state boundaries. tion of vine vigor, were not collected are presented as additional trials at Rootstock evaluation trials oc- during this study because of the re- these two sites were conducted from curred in two locations; Everson, peated summer hedging of the can- 2008 until 2010, allowing for contin- WA, and Mount Vernon, WA (Wash- opy that was done at both sites in all ued temperature monitoring. Average ington State University – Northwest years of the study. This repeated monthly high and low temperatures, Research and Extension Center). practice removed enough biomass to and total monthly precipitation as The soil at the site in Everson is result in no vigor differences between recorded by nearby AgWeatherNet a coarse-silty, mixed, superactive, treatments (data not shown). To eval- stations (Washington State Univer- mesic Fluventic Haploxerolls (pedon: uate sugar content, 10 berries per vine sity, 2018), are presented in Fig. 1. Nooksack silt loam). The soil at the from five vines per treatment replica- The combined vintage and location Mount Vernon site is a fine-silty, tion were arbitrary sampled (50 variation allowed for a fair represen- mixed, superactive, nonacid, mesic berries total per treatment replica- tation of rootstock performance Fluvaquentic Endoaquepts (pedon: tion). Berries were sampled from the across a broad range of sites that are Puget silty clay loam) (USDA, shoulders, middle, and tip of clusters. available in the Puget Sound AVA. 2018). The Everson site is located Berries were crushed in a plastic bag ROOTSTOCK EVALUATION TRIALS. near lat. 48.92 N, long. 122.34 W and collected juice soluble solids Only in 1 year of the study, 2004 (specific coordinates omitted to were measured with a handheld tem- (Tables 2 and 3), and in one location protect private property owner). The perature-compensating refractometer (Mount Vernon, WA), did the use of Mount Vernon site is located at (ATC-1; Atago USA, Livermore, rootstocks significantly increase final lat. 48.4391 N, long. 122.3875 W. CA). The same juice was used soluble solids in harvested fruit. Both vineyards were established in to evaluate pH and TA (Phi 32; Rootstock 420A had significantly 2000, with vine by row spacing at Beckman-Coulter, Indianapolis, IN). higher soluble solids than the self- 5 · 9 ft in Everson and 6 · 10 ft in Titratable acidity was measured by rooted control (20.13% compared Mount Vernon. Vines were planted as titrating 0.1 N sodium hydroxide with 18.00% soluble solids, respec- dormant, rooted cuttings. The vari- (NaOH) solution into 5 mL of tively). This occurred in a vintage that ety-rootstock combinations of Pinot juice diluted with 25 mL of distilled was noted by above-average temper- Noir 02A self-rooted, Pinot Noir 02A deionized H2O until a pH of 8.2 atures. Mount Vernon, WA, was 126 grafted to 420A, and Pinot Noir 02A was reached. Amount of NaOH GDD units above average, whereas grafted to 101-14 Mtg were sourced was recorded, and percent TA was Everson, WA, was 185 GDD units from Duarte Nursery in Hughson, calculated as follows: TA (percent) = above average. Noted by dryer sum- CA. The variety-rootstock combina- 0.15 · mL 0.1 N NaOH used. mer months and where most vineyards tion of Pinot Noir 02A grafted to 3309C was sourced from Sonoma Grapevines, Inc. in Fulton, CA. Vines Table 1. Annual growing degree day accumulation from on-site temperature in both locations were trained to recordings at both the Mount Vernon, WA, and Everson, WA, vineyard locations a double guyot, with a vertical from 2004 to 2007. shoot-positioned trellis system with Growing degree day accumulationz a fruiting wire at 30 inches above the ground, a set of double wires (termed Yr Mount Vernon Everson ‘‘catchwires’’) 12 inches above the 2003 1,965 2,147 fruiting wire, and single wires at 20 2004 1,817 2,075 and 28 inches above the fruiting wire. 2005 1,727 1,897 After fruit set, clusters were thinned 2006 1,600 1,948 to one cluster per shoot, and fruit- 2007 1,499 1,684 zone leaf removal around the clusters 2008 1,523 1,587 was completed. Canopy hedging to 6-year average 1,689 1,890 just above the top catchwire was zGrowing degree day, base 50 F (10.0 C) from 1 Apr. to 31 Oct.
832 • December 2018 28(6) do not have supplemental irrigation, the desired wine style. In general, the The typical juice pH range acceptable this instance of increased soluble solids recommendation soluble solids range for white wine production (without may not be related to advancement of for sparkling wine is 17% to 20%, for requiring substantial amelioration) is maturity, but rather dehydration of white table wine is 19% to 23%, and 3.1–3.4, with red wine musts falling the fruit. In all other years of the study, for red table wine is 20% to 24% in a slightly higher pH range (3.3– which were only slightly above average (Boulton et al., 1996), indicating that 3.6) (Jackson, 2008). When the pH is GDD accumulation to below average chaptalization would be necessary at below that, the must becomes an un- GDD accumulation, rootstock did not these sites for production of any wine suitable environment for Saccharomyces influence final soluble solids accumu- style other than sparkling. cerevisiae yeast, thus slowing or lation in the fruit (Tables 3 and 4). Final juice pH was not influenced stopping fermentation (Ough, 1966). For context, acceptable ranges in sol- by rootstock in either location during When the pH is above that, the juice uble solids content can differ based on any year of the study (Tables 2–4). environment becomes favorable for
Table 2. Comparison of juice quality differences of the wine grape variety Pinot Noir 02A on different rootstocks in 2004. The trial was conducted at two different locations in western Washington state: Mount Vernon and Everson. Date of Rootstocky Location sampling Juice evaluationz 3309C 101-14 Mtg 420A Self Mount Vernon 24 Sept. Soluble solids (%) 16.97 19.36 17.40 15.30 GDD = 1,817x pH 3.04 3.01 2.95 2.84 Titratable acidity (g/100 mL) 0.79 bw 0.85 b 0.86 b 1.32 a 30 Sept. Soluble solids (%) 18.00 ab 18.50 a 18.40 a 16.47 b pH 3.11 3.11 3.09 3.00 Titratable acidity (g/100 mL) 1.09 ab 1.02 a 1.05 ab 1.47 a 14 Oct. Soluble solids (%) 19.67 ab 19.73 ab 20.13 a 18.00 b pH 3.11 3.10 3.14 3.00 Titratable acidity (g/100 mL) 0.91 a 0.94 a 0.92 a 1.26 b Everson GDD = 2,075 27 Sept. Soluble solids (%) 20.07 20.40 19.73 19.53 pH 2.93 2.88 2.93 2.90 Titratable acidity (g/100 mL) 0.94 0.83 0.86 1.03 2 Oct. Soluble solids (%) 21.57 20.90 20.90 20.63 pH 3.14 3.04 3.13 3.12 Titratable acidity (g/100 mL) 0.74 b 0.86 ab 0.80 ab 0.92 a 5 Oct. Soluble solids (%) n/a 21.17 21.23 21.50 pH n/a 2.77 2.84 2.84 Titratable acidity (g/100 mL) n/a 0.74 0.81 0.75 z1 g/100 mL = 1%. y3309 = ‘3309 Couderc’, 101-14 Mtg = ‘101-14 Millardet et de Grasset’, 420A = ‘420A Millardet et de Grasset’, Self = self-rooted control. xGrowing degree days base 50 F (10.0 C) from 1 Apr. to 31 Oct. wValues with different letters within a row indicate significant difference at a = 0.05 (Tukey’s honestly significant difference). GDD = Growing degree days.
Table 3. Comparison of juice quality differences of the wine grape variety Pinot Noir 02A on different rootstocks in 2005. The trial was conducted at two different locations in western Washington state: Mount Vernon and Everson. Date of Rootstocky Location sampling Juice evaluationz 3309C 101-14 Mtg 420A Self Mount Vernon 29 Sept. Soluble solids (%) 18.53 18.53 19.43 17.33 GDD = 1,727x pH 3.23 aw 3.23 a 3.27 a 3.12 b Titratable acidity (g/100 mL) 1.00 b 0.96 b 0.88 b 1.32 a 5 Oct. Soluble solids (%) 19.77 19.67 20.37 18.53 pH 3.15 a 3.14 a 3.17 a 3.02 b Titratable acidity (g/100 mL) 1.06 b 1.09 b 0.99 b 1.46 a 12 Oct. Soluble solids (%) 18.90 18.60 19.73 18.60 pH 3.56 3.59 3.61 3.45 Titratable acidity (g/100 mL) 1.05 b 1.05 b 0.97 b 1.42 a Everson GDD = 1,867 11 Oct. Soluble solids (%) 19.90 19.47 19.93 19.73 pH 3.09 3.16 3.13 3.04 Titratable acidity (g/100 mL) 1.00 0.87 0.91 1.00 z1 g/100 mL = 1%. y3309 = ‘3309 Couderc’, 101-14 Mtg = ‘101-14 Millardet et de Grasset’, 420A = ‘420A Millardet et de Grasset’, Self = self-rooted control. xGrowing degree days base 50 F (10.0 C) from 1 Apr. to 31 Oct. wValues with different letters within a row indicate significant difference at a = 0.05 (Tukey’s honestly significant difference). GDD = Growing degree days.
• December 2018 28(6) 833 PRELIMINARY AND REGIONAL REPORTS spoilage microorganisms. In the two 2008). Although the use of root- did so in some years in Mount Ver- warmer years for Mount Vernon, 2004 stocks decreased TA relative to the non, WA. Over the course of the and 2005, juice pH for all treatments self-rooted control, in cooler vintages study, Everson was warmer on aver- waswithinanappropriaterange TA was still higher than desirable, age (Table 1; Fig. 1) than Mount (Tables 2 and 3). However, in cooler indicating that acid adjustment may Vernon. Both sites would be on the vintages, such as 2006 and 2007, juice be necessary regardless of the use of very low end of Region I of the pH was below the minimum threshold, rootstock. Winkler Viticulture Region scale and pH adjustments in a commercial In 2006, yield was significantly (Amerine and Winkler, 1944). production scenario would be neces- influenced by the use of rootstocks Whereas originally designed to cate- sary to create an environment appro- (Table 5). Self-rooted vines had sig- gorize Californian product regions priate for S. cerevisiae fermentation. nificantly higher yield than any of the and determine varietal appropriate- These results indicate that the use grafted combinations. These differ- ness based on GDD accumulation of these three rootstocks in western ences were not observed in 2007, between bloom and harvest and Washington is an inappropriate cultural and weather conditions were not ex- GDD accumulation the month pro- approach in an effort for adjusting ceptionally favorable for fruit devel- ceeding harvest, its use has been pre-fermentation must pH. opment in that year (i.e., in-season misapplied to categorize site appro- The use of rootstocks consis- heat accumulation was at 1499 priateness over what is considered the tently had a beneficial effect on final GDD). Past studies in Oregon in- entire growing season for most north- juice TA (Tables 2–4), except in 2006 dicate more explicit differences in ern climates (i.e., GDD accumulation in Mount Vernon. In those years yield, with 3309C consistently result- period between 1 Apr. and 31 Oct., where significant differences were ob- ing in overcropped vines (Shaffer rather than phenological stages). served, the self-rooted control had et al., 2004), but this was not seen Subsequent research has refined this higher TA than all the rootstock in our study. Although this limited scale, particularly on the cooler end, selections. In 2006, whereas no sig- study provides some evidence for to demonstrate the appropriateness of nificant differences were observed be- yield management (Table 5), a direct early-ripening wine grape varieties tween the different rootstocks and the comparison of the rootstocks cannot and some hybrids at temperature ac- self-rooted control, the self-rooted be made given that the vines were cumulations between 1500 and 1800 control had the highest overall aver- actively crop-thinned to one cluster GDD (Jones et al., 2010). However, age TA. In this 2006 vintage, all per shoot in all rootstocks and in both that work admittedly included a lower treatments had TA levels that would years where total vine yield was threshold baseline from evidence of be considered unacceptable and in collected. new commercial plantings in cool need of adjustment. Typical juice TA sites (i.e., the Puget Sound AVA), ranges that are acceptable for wine Conclusion rather than on long-term perfor- production (without requiring sub- Throughout this trial, the use of mance of those varieties inclusive of stantial amelioration) are between rootstocks did not influence final har- annual variability in ripening. Since 0.55 and 0.85 g/100 mL (Jackson, vest parameters in Everson, WA, but that publication, though, there has
Table 4. Comparison of juice quality differences of the wine grape variety Pinot Noir 02A on different rootstocks in 2006 and 2007. The trial was conducted in western Washington state at Mount Vernon. Date of Rootstocky Location sampling Juice evaluationz 3309 101-14 Mtg 420A Self 2006 GDD = 1,600x 23 Oct. Soluble solids (%) 19.15 19.20 19.30 18.30 pH 2.76 2.72 2.70 2.63 Titratable acidity (g/100 mL) 1.20 1.17 1.35 1.67 2007 GDD = 1,499 26 Oct. Soluble solids (%) 18.80 19.07 18.60 18.13 pH 3.02 3.02 3.02 2.94 Titratable acidity (g/100 mL) 1.28 aw 1.26 a 1.25 a 1.51 b z1 g/100 mL = 1%. y3309 = ‘3309 Couderc’, 101-14 Mtg = ‘101-14 Millardet et de Grasset’, 420A = ‘420A Millardet et de Grasset’, Self = self-rooted control. xGrowing degree days base 50 F (10.0 C) from 1 Apr. to 31 Oct. wValues with different letters within a row indicate significant difference at a = 0.05 (Tukey’s honestly significant difference). GDD = Growing degree days.
Table 5. Effects of different rootstocks on yield of the wine grape variety Pinot Noir 02A in 2006 and 2007 in western Washington state at the Mount Vernon site. Rootstocky Yr Date of sampling Yieldy 3309C 101-14 Mtg 420A Self 2006 25 Oct. lb/vine 5.28 bx 6.26 b 5.10 b 9.97 a 2007 25 Oct. lb/vine 5.91 3.47 6.42 4.94 z1 lb = 0.4536 kg. y3309 = ‘3309 Couderc’, 101-14 Mtg = ‘101-14 Millardet et de Grasset’, 420A = ‘420A Millardet et de Grasset’, Self = self-rooted control. xValues with different letters within a row indicate significant difference at a = 0.05 (Tukey’s honestly significant difference).
834 • December 2018 28(6) been an increase in successful com- 2003. Rootstock selection, p. 12–15. In: fruit composition of grapes in British mercial production of early-ripening L.P. Christensen, N.K. Dokoozlian, M.A. Columbia. HortTechnology 11:419– winegrape varieties in the region, as Walker, and J.A. Wolpert (eds.). Wine 427. growers have selected sites that max- grape varieties in California. Univ. California Agr. Natural Resources Publ. 3419. Ruhl, E.H., P.R. Clingeleffer, P.R. imize the available GDD for their area Nicholas, R.M. Cirami, M.G. McCarthy, (Moyer et al., 2014; USDA, 2017). Boulton, R.B., V.L. Singleton, L.F. and J.R. Whiting. 1988. Effect of root- There are many tools viticultur- Bisson, and R.E. Kunkee. 1996. Principles stocks on berry weight and pH, mineral ists can use, however, to overcome and practices of winemaking. Chapman content, and organic acid concentrations site limits, inclusive of the adoption of and Hall, New York, NY. of grape juice of some wine varieties. Austral. J. Expt. Agr. 28:119–125. different training systems, site modi- Bremmer, L. and J. Bremmer. 2014. fications, water management through British Columbia winegrape acreage report. Shaffer, R., T.L. Sampaio, J. Pinkerton, controlled irrigation, careful atten- 8 Nov. 2017.
• December 2018 28(6) 835